1. Field of the Invention
The present invention relates generally to fluid delivery devices. More particularly, the invention concerns an improved apparatus having an electrically activated energy source for infusing medicinal agents into an ambulatory patient at specific rates over extended periods of time.
2. Discussion of the Invention
The oral route is the most frequent route of drug administration. Oral administration is relatively easy for most patients and rarely causes physical discomfort. However, many medicinal agents require a parenteral route of administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes in the digestive tract and the liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. Certain classes of new pharmacologic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.
In the past, prolonged infusion of fluids has generally been accomplished using gravity flow means coupled with electronic based controls and typically involve the use of intravenous administration sets and the familiar bottle or solution bag suspended above the patient. Such methods are cumbersome, imprecise and, generally non-ambulatory requiring bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus.
Devices of the character from which liquid is expelled from a relatively thick-walled bladder by internal stresses within the distended bladder have also been suggested for infusion of medicaments. For example, such bladder, or xe2x80x9cballoonxe2x80x9d type devices, are described in U.S. Pat. No. 3,469,578, issued to Bierman and in U.S. Pat. No. 4,318,400, issued to Perry.
A family of highly unique fluid delivery devices has been developed by the present inventor. These novel devices make use of recently developed elastomeric films, expandable foams and similar materials, which, in cooperation with a base define a fluid chamber that contains the fluid to be dispensed. The elastomeric film membrane or the expandable member controllably forces fluid within the chamber into outlet fluid flow channels provided in the device. Elastomeric film membrane devices are described in detail in U.S. Pat. No. 5,205,820 issued to the present inventor. U.S. Pat. No. 5,468,226, also issued to the present inventor, describes various types of expandable cellular elastomers and elastomeric foams used as the energy source of the fluid delivery device for expelling fluid from various physical forms of the fluid delivery device. Because of the pertinence of Pat. Nos. 5,205,820 and 5,468,226, these patents are hereby incorporated herein by reference in their entirety as though fully set forth herein. U.S. Pat. No. 5,961,492 entitled Fluid Delivery Device with Temperature Controlled Energy Source, in which the present inventor is named as a co-inventor, is also incorporated by reference as though filly set forth herein.
The apparatus of the present invention, comprises a unique implantable unit that makes use of novel electrically activated expansive material as an energy source. The apparatus of the invention can be used for the continuous infusion of a variety of beneficial agents as, for example, heparin, morphine, insulin and like agents.
It is an object of the present invention to provide a technically advanced, fluid delivery apparatus for infusing medicinal fluids into a patient that is of a compact, low profile, laminate construction. More particularly, it is an object of the invention to provide an apparatus of such a character which is implantable into the patient""s body and includes a novel expanding polymer gel material which uniquely functions as an internal energy source for expelling the medicinal fluids from the device.
Another object of the invention is to provide an implantable fluid delivery apparatus that can be used for the precise infusion of various pharmaceutical fluids into the patient at controlled rates over extended periods of time.
Another object of the invention is to provide an apparatus of the forementioned character which is of a simple construction and is highly reliable in operation.
Another object of the invention is to provide an apparatus that embodies as its stored energy source, a soft, pliable, semi-solid, electroresponsive mass which is acted upon by an electrical stimulus in a manner to controllably expel fluid from the device.
Another object of the invention is to provide an apparatus as described in the preceding paragraph in which the electroresponsive mass is specifically tailored to provide precise, predictable protocol delivery of the medicinal agent stored within the reservoir of the device.
A further object of the invention is to provide a low profile, readily implantable fluid delivery device of laminate construction which can meet even the most stringent fluid delivery tolerance and flow signature requirements.
Another object of the invention is to provide a fluid delivery device of the type described that includes filling means for initial filling and subsequent refilling of the reservoir to enable continuous operation.
Another object of the invention is to provide an apparatus of the character described which is responsive to an external source of electrical stimulation, and includes a three-dimensional polymer network which functions as a stored energy source that can be constructed from various types of polymeric materials such as polyacrylamide gels.
Another object of the invention is to provide stored energy sources of the character described in the preceding paragraph which comprise blends or laminate constructions of phase transition gels that will enable the achievement of multirate delivery protocols.
Another object of the invention is to provide an apparatus of the character described which includes a novel, combination filter and rate control assemblage disposed intermediate the fluid reservoir and the outlet port of the device or intermediate outlet port of the device and the infusion means.
Another object of the invention is to provide an implantable device having an expandable gel which functions as an internal energy source that includes sensor means for sensing physiological changes in the patient""s body.
Another object of the invention is to provide an apparatus of the character described which, due to its unique construction, can be manufactured inexpensively in large volume by automated machinery.
Other objects of the invention will become apparent from the discussion which follows.